This invention relates to a catalyst particularly suited for use in catalyzing the liquid phase reduction of glycolic acid to ethylene glycol.
It is known to produce ethylene glycol by the liquid phase direct hydrogenation of glycolic acid in the presence of a catalyst as described, for example, in U.S. Pat. No. 2,607,805. It is also known to use metallic cobalt, either alone or in combination with various metal additives, as a hydrogenation catalyst as described, for example, in U.S. Pat. Nos. 2,322,099; 3,260,683; 3,478,112; 3,772,395; and 3,848,003.
Glycolic acid, however, tends to react with metallic cobalt to form cobalt glycolate. Although the cobalt glycolate may be reduced under typical hydrogenation reaction conditions with redeposition of cobalt metal, it has been observed that the catalytic activity of the redeposited cobalt metal is diminished resulting in decreased yields of and decreased selectivity to ethylene glycol.
In order to minimize the extent of reaction between metallic cobalt and glycolic acid, it is desirable to provide a cobalt-based catalyst that would enable conversion of glycolic acid to ethylene glycol in as short as possible a reaction time.